The present invention relates generally to principles of photogrammetry, electronics and computer technology and more particularly to means for measuring the human foot in order to determine a specific shoe size with a degree of accuracy considerably greater than that achieved by technology of the prior art.
More specifically, this invention relates to an apparatus containing a light source which is arranged to cause an outline of a foot to be displayed upon a translucent screen whereby photo-optic principles are employed to direct an image of the outline to the surface of an electronic device containing a monolithic array of light sensitive semiconductor elements which sense strong or weak impulses of energy and inherently discriminate this information into a distinct white/black, light/dark status or relationship to create an electronic duplicate of the foot outline. The electronic image of the foot can then be processed according to a predetermined algorithm so as to determine the shoe size that would provide the best fit. It will be noted that the number of light sensitive elements available with the advanced technology described herein is well beyond that achieved by the prior art. The resolution of status thus obtained accomplishes a precision of measurement never before made possible.
In the past, a number of patents have been issued relating to apparatus for determining sizes of shoes. For example, U.S. Pat. No. 2,975,519 to Berlin confronts the problems of selling shoes by catalog or retail outlet and describes an apparatus wherein a light source is directed toward an opaque plane containing a series of holes strategically placed so as to correspond to the longest and widest portions of an average foot of various sizes. It should be noted that an improper size would be indicated if the longest or widest portion of a given foot does not conform to this average. Thus, a foot of average proportions, even though properly placed in the apparatus, could prevent the light rays from reaching some of the photo-voltaic cells under each of the holes. An arrangement of stepper relays, linkages and print wheels is then used to print the shoe length and width, as determined by the light and dark photo cells, on an order blank. The customer then completes the order blank with his name, address, desired shoe style and color. It is noted that this invention projects a light source in a direction vertical to the plane of the bottom of the foot as opposed to parallel to that plane.
Cohen and Blivice, in U.S. Pat. No. 3,457,647 point out difficulties encountered when using mechanical means that physically touch a foot and compress human tissue. The problem is exacerbated because of further difficulty in determining the exact moment when physical contact has been made between the mechanical means and the foot.
In U.S. Pat. No. 3,328,882, a reference closely related to Cohen, et al '647, a number of light sources and corresponding photo cells are placed in a plane parallel to the bottom surface of the foot and arranged in a matrix such that one set of lights and photo cells is along the length axis of the foot and another set is along the width axis. A properly placed foot would then block some of the cells in each axis and this information is then used to determine the proper length and width shoe.
Cohen et al '647 then state that the large number of photo cells are prohibitive from a cost standpoint and describe an alternate apparatus where only one photo cell (or light source, depending on relative cost) is used per axis and it is moved by motor means along its respective axis until the light path is no longer blocked by the foot and the motor and photo cell is stopped at this position. The position of both motors is tracked by a moving brush contact on a series of contact segments on a printed circuit board surface. The contact closures thus obtained are then encoded by use of a diode matrix and discrete electronic components to display a shoe size and width by illuminating a corresponding set of lights on the apparatus panel. A special-lamp indicates sizes greater than 15 in length or width of EEE.
Greensides U.S. Pat. No. 3,931,681 uses virtually all mechanical means to determine length, width and girth at a point 72.5% of the length as indicated by motorized pointers on a tape measure type scale. This arrangement suffers from the previously mentioned problems of determining an exact point of physical contact on a foot and requires a large number of moving parts.
Baumann, U.S. Pat. No. 4,294,014 states that all of the previous art suffers from the shortcomings of numerous moving parts (stepper relays, printers, brush contacts, motors, etc.) all of which are subject to wear, faulty operation and ultimate failure. Baumann, '014 pinpoints the major source of measurement error shown in prior art as interference caused by light sources adjacent to the light source corresponding to a particular photo cell and the errors caused by effects of incident light and diffraction.
Baumann '014 suggests other forms of radiant energy may be used, such as electromagnetic or sound, and describes a preferred embodiment consisting of infra-red emitters and opposing infra-red sensors arranged in a matrix corresponding to the length and width of the foot and in a plane parallel to the bottom of the foot. This is similar to Ser. No. 346,601 mentioned by Cohen and Blivice, now U.S. Pat. No. 3,328,882, but is now more practical because present day technology has made infra-red devices available at a cost which makes this configuration attractive. This concept would be prone to the error sources described by Baumann except for the sophisticated time division multi-plex and modulation techniques employed whereby only one light source is activated at any one time and the light source is modulated in such a way that only receivers modulated in the same manner will respond to the light source. These techniques are now common and practical in optical emitting and sensing applications. It should be noted the Baumann apparatus measures a shoe size based only upon the maximum length and width measured, with no determination made as to where exactly the maximum occurs.
It is further noted that none of the prior art is suitable for using computer interface technology to measure the size of a foot and also to maintain inventory, predict market trends, automate ordering, or in general acquire data for statistical purposes to advance the art of shoe making.